Interesting
I'm just thinking simple but you might have a better idea already.
But why not just turn the bolt & trunnion upside down like the AK47 design? Your thinking of taking off the recoil spring part off the top so that will be facing down now.

I'd think the hardest parts would be setting up the side mounted recoil springs and hammer?

"Government is not the solution to our problem, government is the problem" Ronald Reagan

I was moving the springs to the sides to clear a path of travel for the hammer. The reason I want to try to keep everything right side up is to hopefully reduce any extraction issues the design might have, as well as leave the option to use the butt-ton of G3 mags I have in an IMI Negev setup.

The H-21 type uses sprockets like a six pointed star to feed the belt across the feed plate. Two such sprockets on a small shaft are rotated by a vertical acting lever which is cammed downward by the bolt carrier tail end.

wanna sell that extra barrel? hehe anyway i've actually been having some of the same thoughts in my mind (home brew cetme beltfeed that is) an idea i had was removing the the charge tube part on the blot carrier turning the bolt, carrier and trunnion upside down and having either the dual springs or lengthening the rear of the receiver to fit a spring that would have a spacer tube with a groove for the hammer like the semi mg42 builds. i kinda like the mg42 spring idea and without the the charge handle tude part on the carrier a receiver could be made from a long tube with weded in rails heck make it long and have a barrel shroud. then maybe use an mg3 top cover and feed tray and weld on a lug on the bc to run the feed mech and as far as the ejector somehow mount it on the underside of the top cover i guess it would be an interesting looking gun and if anyone knows anywhere i could have a chamber fluted without my wife skinning me when she see's what I've paid then i would try building this exact idea only in 8mm with like a mauser take off barrel hehe then you could always take off the top cover and feed tray and put on an addapter like the hk 21 had and have top mounted mags or something like that. anyway i'm not trying to hyjak your idea too much but i got excited. i like your idea of making the bolt feed from the top or bottom, hmmm i'll have to stare at my bolt and carrier for a while and think hmm you might have problems ejecting cases if you put a feed tray on top and dont turn your bolt and carrier upside down, I'll be watching this thread, if i can help in any way i'd love to but i'm afraid the only think i know about building hk's is from reading tutorrials and staring at my cetme kit

That's cool I had a feeling you wouldn't want to sell your extra barrel haha. All those ideals I posted earlier I've consolidated and am going to make myself a belt fed cetme based rifle too, I figure I'll use my one semi modded grip and fcg on my belt gun and someday my regular cetme, that way the only extra cetme parts I need to buy are trunnion, bolt/carrier and butstock/mount. if my plan works it will be like a weird child of a cetme mother and an mg 42 father haha. I'll probably use an mg42 barrel and try making it 8mm as well

Hello jreifsch80,
It seems that you are trying to re-invent the German WW-II MG-42V. It was a simplified MG-42 using the roller delay lock system of the StG-45M (today's HK and CETME). Some were built in Switzerland after the war as the SIG 710 series. The recoil spring is behind the bolt/carrier as was the StG-45M prototype. Cool concept !!!

Yeah viper your right I guess, I don't know why I didn't catch that either. I love mg42's (m53's are more my price range) but my "mg45" type idea is more reasonable (probably money wise but maybe not time wise) then even an m53. I've even placed this idea on the front burner and will aquire the needed parts as soon as I have the extra money in a few weeks. I need to research the mg45 more hehe anyone know where to find pictures if there are any? Maybe I'll drill a hole through the bolt and bolt carrier for an mg42 type ejection where a rod is pushed forward to knock the case out haha maybe not I might make it too coplicated to ever fet it finished. Anyway I've hyjacked this thread long enough, I'm tying to think of how the mg3 feed prawl system can be driven without the long drive channel thing that is almost the length of the top cover. Then a guy could use a moddified mg3 cover and feed tray upside down for a poor man's hk21 type rifle, maybe a couple of L shaped levers and springs when the carrier recoils back and a spring to return them after the bolt and carrier come to rest in battery. Hmmm I'll have to chew on this idea and see what there's room for between the feed tray and trigger group when I eventually get my parts.